The present invention relates to valves for fluids and more specifically to valves suitable for construction as high flow, high-pressure microvalves.
Small fluid valves are known in the art that have been developed using Micro-Electro-Mechanical-Systems (MEMS) concepts. These small-scale valves have the advantage of being able to be produced very precisely and inexpensively using fabrication techniques more commonly used in the microelectronics industry. Typically, such valves also consume very low power and have high switching frequencies. While these valves have many ingenious configurations, most are limited to low pressures, e.g., under 200 psig (approximately 1,500 kPa), and all are limited to extremely low flows, e.g., under 10xe2x88x924 kg/second. In fact, none of the actuation mechanisms known, such as electromagnetic, electrostatic, piezoelectric, and shape-memory alloys, are capable by themselves of producing both the forces necessary to overcome high pressures, and the deflections needed to provide large flow areas.
It is an object of this invention to provide a means for switching high flow rates at high pressures, at the expense of response time, by a device that is particularly suitable for fabrication using micro-fabrication techniques.
The present invention is a two-stage valve for controlling the flow of fluid, typically a gas from a pressurized gas supply, comprising an upper main body including a cavity therein, the cavity including an inner surface; a lower main body having a plurality of pressurized gas supply exhaust outlet passages forming a primary flow path with the pressurized gas supply, the primary flow path including an inlet passage for the flow of gas from the pressurized gas supply; a pre-stressed diaphragm sandwiched between the upper and lower main bodies, the pre-stressed diaphragm having an upper surface opposite to the inner surface of the cavity in the upper main body, the pre-stressed diaphragm having one side of a portion thereof in fluidic communication with the cavity, and the opposite side of the portion thereof in fluidic communication with the pressurized gas supply, the inner surface of the cavity being contoured to correspond with the upper surface of the pre-stressed diaphragm; and pressure control means fluidically coupled to the cavity for controlling the pressure in the cavity to cause the portion of the pre-stressed diaphragm to open the flow of gas from the pressurized gas supply through the primary flow path of the two-stage valve and to cause the portion of the pre-stressed diaphragm to close the flow of gas from the pressurized gas supply through the primary flow path of the two-stage valve, at least a portion of the inner surface of the cavity in the upper main body providing a resting surface for the upper surface of the pre-stressed diaphragm, at least one of the plurality of supply fluid exhaust outlet passages being directed such that a component of supply fluid exhaust outlet velocity is in a direction opposite to a component of supply fluid exhaust outlet velocity in at least one other of the plurality of supply fluid exhaust outlet passages.
The pressure control means comprises the lower main body having a secondary flow path communicating with the pressurized gas supply, the upper main body having a secondary flow path communicating with the secondary flow path in the lower main body, and communicating with the cavity in the upper main body; a first valve providing (a) an isolating means for isolating the flow of gas from the pressurized gas supply to the cavity in the upper main body, and (b) an opening means for allowing the gas from the pressurized gas supply to flow to the cavity in the upper main body, the upper main body having an exhaust passage for fluidically communicating the cavity with an environment at a pressure lower than the pressure of the pressurized gas supply, a second valve installed in the exhaust passage, the second valve providing an isolating means for fluidically isolating the cavity in the upper main body from the environment, and an opening means for opening the cavity in the upper main body to exhaust to the environment.
The first valve is installed in one of (a) the secondary flow path in the lower main body, and (b) the secondary flow path in the upper main body. The lower main body can include a cavity. The lower main body further can include a boss formed in the cavity of the lower main body, the boss surrounding a hole acting as the inlet passage for the flow of gas from the pressurized gas supply, the hole fluidically coupled to the opposite side of the portion of the pre-stressed diaphragm. Preferably, the boss formed in the cavity of the lower main body is positioned coincident with the center of the cavity of the lower main body. The inlet passage from the pressurized gas supply can be directed in a direction substantially perpendicular to the pre-stressed diaphragm. The valve has a form factor F defined as a height H/length L wherein the form factor F is not greater than 0.1. The diaphragm is comprised typically of titanium.